Via Yahoo! News, "For a cluster of lakes in Australia's eastern Victoria, the combination of the fire and then the rain washed ash and nitrogen-rich soil into the water. The Gippsland Lakes experienced a rise in sea level. That caused the lakes to mix with sea water, which also raised the salinity.
This recipe led to the introduction of a species of algae called Noctiluca scintillans, commonly known as "sea sparkle." The bioluminescent brew gave the water a nocturnal glow."